When a bug is found in firmware after embedded devices have been released, it is common practice to solve the problem by overwriting the old firmware with firmware in which the bug has been fixed. The term firmware as used herein refers to all the data that is pre-stored in a non-volatile storage area of an embedded device. As documents relating to such firmware updates, there are, for example, Patent Document 1 and Non-Patent Document 1.
Patent Document 1 is a firmware updating method in which firmware is replaced entirely. Since firmware is replaced entirely, if an update were to be performed via a network, all firmware images of the new version would have to be distributed, and the size of the data to be distributed would thus become large.
Further, Non-Patent Document 1 is a technique for extracting the difference between an old version of data and a new version of data. In updating firmware via a network, it is possible to reduce the size of distributed data by distributing only the updated difference in firmware using this technique.